1. Technical Field
The invention relates to the art of fluid pressure devices, and more particularly, to an air spring formed of a tubular elastomeric sleeve or bellows wherein one end of the bellows is reinforced with elastomeric strips containing biased reinforcing cords to stabilize the air spring and prevent the bellows from rolling over the end closure.
2. Background Information
Air springs are well known in the art and comprise an elastomeric sleeve or bellows which is maintained between a pair of end members, one of which is usually a piston at one end and an end cap assembly at the other end. Such air springs are used primarily for implementation in motor vehicles for supporting the vehicle body or for use in other types of equipment subject to shock to provide cushioning therefor. The air springs are sealed at the ends to form a pressurized fluid chamber within the bellows. Upon the air spring experiencing a road shock, the bellows will begin to collapse as the end members move toward each other, with one end of the bellows rolling along or over the sidewall of the bottom piston member to yield predictable dynamic characteristics. However, if the bellows of the air spring rolls over the bead plate at the opposite end instead of along the sidewall of the piston, the dynamic characteristics will be adversely effected. Also, the life of the air spring will be materially reduced.
The diameter of the piston is restricted by the diameter of the opposite end bead plate, and the larger the end bead plate, the more difficult it is to prevent the bellows from rolling over the edges of the plate, and in particular, the inturned peripheral clamping edge thereof. Therefore, to prevent this rollover effect, external rings or special mountings have heretofore been required to stabilize the air spring, which added to the cost and weight of the air spring. Other types of reinforcements use thicker rubber or additional rubber strips in the area of the bellows adjacent this end plate or end cap in order to stiffen this area to prevent end plate rollup.
In addition to the above-described prior art structures to eliminate end plate rollup, the following patents set forth below, disclose additional prior art of interest to the present invention.
U.S. Pat. No. 2,920,885 discloses a reinforcing air spring wherein the body includes reinforcing elements embedded in the walls which are anchored at the bead cores. The ends of the reinforcing elements are wrapped around the bead cores to form a double ply at each end. Such construction is not believed to prevent rollover at the ends of the bellows, but are used to enhance the strength characteristic at the bead area.
U.S. Pat. Nos. 2,996,103 and 3,666,598 show various types of apparatus for making air springs, neither of which disclose any particular construction for stiffening the area of the bellows adjacent the end bead thereof as does the present invention.
U.S Pat. No. 3,043,582 discloses a rolling lobe air spring wherein the layers of material are wrapped around the bead rings, but does not disclose any construction to prevent the bellows or membrane from rolling upwardly over the end plate.
U.S. Pat. No. 4,174,827 is an example of one of the prior art air springs which provides a collar or additional structural component external of the air spring, to prevent the bellows from rolling upwardly over the end ring or clamping plate.
U.S Pat. No. 4,763,883 discloses an air spring bellows construction wherein the bellows is formed of elastomeric material and reinforced with embedded fiber cords. Successive layers of cord are wound in annular bands, either in the rolling lobe or in the chamber portion, in combination with helical windings to change angles of the cord material.
U.S. Pat. No. 3,319,952 is believed to be one of the closest air spring construction to that of the present invention. This patent discloses reinforcing strips beneath the clamp area for reinforcing the clamp area, but does not show reinforcement located adjacent the clamped area in the body of the bellows to prevent the bellows from rolling over the clamped area at the end plate.
None of these prior art patents discussed above, disclose the present invention of stiffening one end of the bellows adjacent the end plate to sufficiently stiffen the bellow without materially adding to the weight thereof, to prevent rollup over the end plate.